Processing of plywood panels to emboss one face thereof



NOV. 30, 1954 R, LEW|5 ErAL 2,695,857

PROCESSING OF PLYWOOD PANELS TO EMBOSS ONE FACE THEREFOF Filed Nov. 12, 1949 2 Sheets-Sheet l Gttorneg Nov. 30, 1954 R. L Ewls ETALl PROCESSING oF PLYwooD PANELS To EMBoss oNE FACE THEREEOF Filed NOV. 12, 1949 2 Sheets-Sheet 2 Z Gttorneg Patented Nov. 30, 1954 PROCESSING 0F PLYWOOD PANELS TO EMBOSS ONE FACE THEREOF Rehbock Lewis, South Pasadena, and Clifford T. McElroy, Temple City, Calif., assiguors, by mesne assignments, to Sierra Lumber Products, Pasadena, Calif., a corporation of California Application November 12, 1949, Serial No. 126,724 7 Claims. (Cl. 154-106) This invention relates to the processing of plywood panels to provide embossments on one outer face thereof.

Plywood panels comprise three or more plies and in commerce are produced in several grades, the gradings being determined by the proportion, to the area of a panel, of the total area of voids in the inner or bottom plies. Such voids, in the main, result from knots becoming dislodged. The better grades of panels have no or fewer knot-holes. It will be evident, however, that the better grades of panels are the more expensive and most difficult to produce because of the great amount of sorting and care attending the manufacture.

The present invention contemplates embossing the outer face of the upper ply of a plywood panel to provide a decorative construction or wall-lining element. The major problem attending the production of embossed panels results from the mentioned knot-holes, since the embossing pressure employed tends to inwardly flex those portions of the upper ply that are above the knot-holes. Consequently, said portions do not take the embossments and the panel is strewn with. a multiplicity of smooth or bald spots, rendering the same unsightly. Of course, knot-hole-free panels would give desired results, but the expense involved in first paying the increased cost of such high grade panels and the further expense attending careful inspection, as by fluoroscoping, to discover such knot-holes that may be present even in high grade panels, raises the cost of the product so that the same cannot economically compete on the open market.

An object of the present invention, therefore, is to provide a novel method and apparatus for producing properly embossed panels regardless of the number and size of the knot-holes in the inner and lower plies to thereby provide a desired product at relatively low cost.

As a result of the present embossing method, not only the depressed portions of the upper ply are hardened. but also the raised portions are compressed to be harder than the original hardness of the panel. The above is in contradistinction to results obtained by prior methods, either by embossment or by removal of material to leave alternate high and low areas or stripes.

Another object of the invention, therefore, is to provide novel and improved apparatus for producing an embossed plywood panel which has an outer face, all portions of which are harder than the initial or original hardness of the outer ply of the panel.

A further object of the invention is to provide an embossed plywood panel in which the embossments are uniformly impressed throughout the entire surface thereof and which is adapted to be produced in a continuous commercial process at low cost.

The invention also has for its objects to provide such means that are positive in operation, convenient in use, easily installed in a working position and easily disconnected therefrom, economical of manufacture, relatively simple, and of general superiority and serviceability.

The invention also comprises novel details of construetion and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. However, the drawings merely show and the following description merely describes one embodiment of the present invention, which is given by way of illustration or example only.

In the drawings, like reference characters designate similar parts in the several views.

Fig. 1 is a cross-sectional view of apparatus embodying novel features and adapted to produce plywood panels according to the present invention.

Fig. .Z is a vertical sectional view of the machine shown in Fig. l, together with a schematic showing of means for heating a portion of said machine.

Fig. 3 is an enlarged sectional view showing an old and usual method for embossing, and indicating how an unembossed area will result above a knot-hole in the middle ply of a three-ply panel being embossed.

Fig. 4 is a similar view, the same being taken on line i-t of Fig. 2, and indicating how the present means will eifect proper embossmcnt of an area above a comparable knot-hole.

F.Fi 5 is a sectional view as taken on line 5 5 of Fig. 6 is a view similar to Fig. 4, and indicating the parts in the position they assume when the bottom ply of the panel contains a knot-hole.

Fig. 7 is a further enlarged sectional View, showing the manner in which the entire embossed surface of the panel is hardened during embossment.

The apparatus shown in Figs. l and 2 comprises, generally, a machine having rolls lil and 11 between which a plywood panel l2 is adapted to be passed, means 13 optionally provided, for straightening the panel after embossment thereof, and means 14 for supplying heated fluid to roll lll. One or both rolls may be driven so as to eflect feeding of a panel therebetween. A generally conventional support frame i5 for the rolls includes upper bearings 1.6 for roll itl and adjustable bearings 17 for roll il. Adjustable pressure between the rolls is afforded as by adjusting screws 1S engaged with bearings 17.

While the roll il has solid trunnions 19 that engage in bearings 17, roll l@ is provided with hollow or tubular trunnions Ztl that communicate with the hollow interior 2l of the latter roll. A swivel 22 extends from each trunnion Ztl and said swivels are connected, by conduit lines 23, to the heated-fluid supply means 14. ConseA quently, a continuous supply of hot oil 24, maintained at approximately 500" F. to be a little below the ilash point, is circulated by means 14 through the hollow' 2l of roll 15J* to heat the cylindrical Wall 25 of said roll.

Roll lt) is made of a suitable metal such as iron or steel and, in practice, cylindrical wall 25 is relatively thick for the dual purpose of imparting non-sagging rigidity to the roll, and absorbing and retaining heat supplied by the hot oil 24. The outer surface of roll wall lll is provided with a series of circumferential lands 26 (Fig. 4) that may be formed in accordance with the design desired to be impressed into the panel 12. Said ridges may be continuous or interrupted; uniform or variable; and deep or shallow, according to the design desired. in any case, all or a major portion of said .lands 26 are rounded in cross-section as are also the grooves 27 that alternate with the lands for reasons later apparent.

Roll 1.1 may be solid but is preferably hollow to avoid excess weight, the cylindrical wall 28 thereof being thick as before. According to the invention, said roll l1, about its wall 28, is provided with a layer 29 of a resilient material that, rather than being merely compressible, is also owable. Certain synthetic rubbers 'have the property of being substantially non-compressible when confined. However, when unconned, pressure against one portion will cause compression of that portion and result in ad jacent portions becoming expanded due to a flow or displacement of material. Such materials are substantially non-porous and are of the type that may be advantageously employed as layer 29.

The present invention is described with respect to a three-ply panel, since such panels are in greater use than panels having more plies and which may be han dled by the present apparatus in the same manner. As illustrated the panel 12 comprises an upper ply 30, a bottom ply 31, and a middle ply 32. For reasons of clarity of description, the upper and lower plies are differentiated although they are usually similar outer plies. In their manufacture, due care is taken to have at least one outer ply free of knot-holes. ly, except in the highest grades, the middle ply and, to

, a lesser degree, one of the outer plies, may have one or more knot-holes` therein as hereinbefore indicated.

Consequent- Referring now to Fig. 3, in which a conventional panel\12 is shown-inthe process of being embossed under pressure from elements 33 and 34, it will be seen that the portion 35 of ply 30 that is immediately above knot-hole 36, is unsupported.. Consequently, the ernbossing lands 26, rather than impressing on the outer faceofply l30, depress said ply portion 35 into the void of the knot-hole. If the void 36 is in the bottom ply, the middle ply would offer little more effective support for the ply being embossed. Thus, such a panel would be defective in that, wherever there was a knothole, there would beeither an unembossed area or a very shallow embossed area that interrupts the continuity of the embossments.

With. more particular reference to Figs. 4 and 5, it will be seen that theportion 35 of ply 30, in the case of a knot-hole 36 in the middle ply, is firmly supported bythe` opposite portion 37 of the bottom ply 31. The heat from wall is more readily transmitted to ply portion 37, than to other portions of ply 31, through the knot-hole. Therefore, because of moisture contained in said portion, the same is rendered more ilexible than normal. Now, when a suitable pressure is applied, as by screws 18, to cause compression of roll layer 29, that portion of said layer which is directly beneath plyportion 37, will swell or expand and displacey said portion in a direction toward ply 30. For all practical purposes, the expanded portion 38 of layer 29 is confined against further flowability or displacement by` adjacent compressed portions of said layer. Hence, the practically incompressible thickened portion 38fsupports inwardly flexed ply portion 37 and the latter, in turn, supports ply portion 35 so that the outer face of the latter will be embossed by lands 26 in the same manner and to substantially the same degree that the remainder of ply is embossed.

The pressure that is applied between rolls 10 and 11 is in excess ofthat necessary for effecting proper ernbossment. This excess pressure manifests itself in considerable compression of layer 29 so that desired ex pansion of the portion 38 thereof is obtained.

As the panel 12 moves past the line of pressure application, such displaced portions 37 will spring back to approximately a coplanar alignment with the remainder of ply 31. It would not materially affect the panel shouldthe return of portion 37 not be complete, since an almost imperceptible indent in the back panel wouldy be the only result. Also, should ply part be moved slightly toward ply part 37 in the process of embossing, an imperceptible shallowing of the embossments may result that would be immaterial to the general perfection' of thepanel.

From Fig. 6 it will be seen that a knot-hole 39 in the bottom ply will admit the expanded portion 38 of layer 29 to thereby support the middle ply 32 which, in turn supports the ply 30Ythat is being embossed.

FromA Fig; 7 it will be evident that lands 26 compress thebres of ply 30 as indicated at 40. Those portions of said ply are, therefore, rendered harder than the initial hardness of saidv ply. The heat transmitted by wall 25, not only converts such moisture that may be present` in ply.30finto steam to temporarily soften the ply to more readily be impressed by lands 26, but there is a dislodgement of both the wood fibres and the resin distributed among said fibres. While the libres may be compressed, the resin, being substantially non-com pressible, can only be displaced. Since this resin is displaced. from beneathl lands 26, it can only flow into those portions of-the ply that are opposite the grooves 27 between the lands. Consequently, the high portions 41 of the embossments have an abnormally high resin content and are, therefore, also harder than the initial hardness ofthe` ply. Since portions 41 are thoseexposed to greatest wear, such increased hardness improves the wear-resisting properties of the panel'. The arrows shown. inFig. 7 suggest the direction ofthe forces that result' in hardening of the ply.

Because of'the compressibility of layer 29, as the panel 12 passes between the rolls 11 and 12, said layer, seeking to--expandsafter compression, tends to curl the panel upward. The means 13 is provided for resisting and-*offsetting any' curl that may thus tend to form. Said means may vary but, as shown, comprises a shoe 42"engaged with the face of thel panel', one on each be varied as by one or more pressure screws 44 to offset the tendencyof the 'panel Yto curl as caused 'by compressive force on liner 29.

It will be seen that the present method obviates damage to the adhesive bonding the plies which may result in undesired blistering. Since, except at the high points of lands 26, .theembossing pressureresults inV a lateral displacementof'mostof' the wood fibres and of the heat-softenedresins, there is little pressure directlytoward the adhesive line that may tend vto break the bond.l

While the invention that has been illustrated Vand described is now regarded as the preferred embodiment, the construction is, of course, subject to modifications without departing from the spirit and scope ofthe invention. lt is, therefore, not desired to restrict the invention to the particular form of. construction illustrated and described, but to cover all modifications that may fall within the scope of the appended claims.

Having thus described the invention, what'is claimed and desired toy be ysecured by Letters Patent is:

l. The method'for embossing only the upper surface of a plywood panel'thaVhas one ormore knotholes in one of the plies other than the top` ply, consisting in subjecting the plywoodv panel to rollerv pressure to effect an embossment on' the upper surface'of thepanel, while atlower roller having a resilient surface issubjected to opposing pressure sufficient to simultaneously and temporarily largely fill the knot holes to. support the upper surface substantially inflexiblyv during: embossing.

2. The method for embossing only the upper surface of a three plywood' panel that has one or more knotk holes in theintermediate ply, consisting in subjecting the panel toroller pressure, to effect'an embossment on the upper surfaceof the panel, while a lowerzroller having a resilient surface is subjected tol opposing pressurey sufficient to simultaneously and temporarily urge the-portion .of the bottom ply underlying the knot hole' into said knot hole. to largely fill the same and cause the upper surface of the bottom ply to contact the bot tom face` of the top ply in order to support the top ply during embossing.

3. The vmethod-according. to claim 2 in which heat is applied to the ply being embossed and transmitted thereby through theknot hole to the bottom ply hav ing the portionthat is displacedto soften said portion for'ready displacement into the knot hole by said -fopposing pressure.

4. The method according to claim' 2 in which heat is applied to the ply being embossed to a degreesuf# iicient to convert moisture in' said ply into steam to temporarily soften' said ply for ready compression and displacement of the wood fibres thereof while the same is being embossed.

5. The method for embossing` the upper surfacel of a multi-ply plywoodpanel while leaving the lower sur` face substantially straight and unembossed', consisting` in passing said panel` betweenl a hard embossing roll and a plane roll covered with a substantially non-compressible, but owable material, andy applyingI sufficient' pressure between said rolls to cause said material to ow to unsupported locationsfwhere' knot holes occur in the other plies below the upper ply' in order to substantially uniformly support the upper ply duringembossing of the upper surface.

6. The method for embossing the upper surface offa three plywood panel having one orl more knot holes in the intermediate ply while leaving the lower'surfacc substantially straight andy unembossed, consisting in passing said panel between a hard fembossing roll"`an`d*a plane roll covered with a substantially non-compressible, but flowablel material and applying sufficient pressure between said rolls" to cause said material to flow tothe 7. The method' according. to' claim 6; in which; heat.

is applied to the upper ply duringemb'ossing for transmission through the knot holesv to"'thev portions of'the 5 bottom ply that are displaced in order to soften said Number portions for ready displacement into the knot holes. g References cited in the me of this patent 9021032 UNrrED STATES PATENTS 5 211621889 Number Name Date 292,572 Parker Jan. 29, 1884 Number 366,755 Baker July 19, 1887 12,527

sep. 21, 1926 Horine Mar. 21, 1933 Hol-mel June 20, 1939 FOREIGN PATENTS Country Date Great Britain of 1910 

1. THE METHOD FOR EMBOSSING ONLY THE UPPER SURFACE OF A PLYWOOD PANEL THAT HAS ONE OR MORE KNOT HOLES IN ONE OF THE PLIES OTHER THAN THE TOP PLY, CONSISTING IN SUBJECTING THE PLYWOOD PANEL TO ROLLER PRESSURE TO EFFECT AN EMBOSSMENT ON THE UPPER SURFACE OF THE PANEL, WHILE A LOWER ROLLER HAVING A RESILIENT SURFACE IS SUBJECTED TO OPPOSING PRESSURE SUFFICIENT TO SIMULTANEOUSLY AND TEMPORARILY LARGELY FILL THE KNOT HOLES TO SUPPORT THE UPPER SURFACE SUBSTANTIALLY INFLEXIBLY DURING EMBOSSING. 